Role of Vector Interaction and Axial Anomaly in the PNJL Modeling of the QCD Phase Diagram

TL;DR

This paper investigates how flavor singlet vector interactions and axial U(1) breaking affect the QCD phase diagram within the PNJL model, revealing that strong vector couplings can eliminate the first order phase transition and align with lattice QCD results.

Contribution

It introduces a consistent cutoff scheme to study the impact of vector interactions and axial anomaly on the QCD phase diagram in the PNJL model, highlighting the conditions under which the first order transition disappears.

Findings

First order chiral phase transition vanishes at large vector couplings.

Critical point disappears for sufficiently strong vector interactions.

The model's results are consistent with lattice QCD at imaginary chemical potential.

Abstract

Effects of a flavor singlet vector interaction in the Polyakov - Nambu - Jona-Lasinio (PNJL) model are studied in combination with the axial U(1) breaking Kobayashi - Maskawa - 't Hooft interaction. Using a consistent cutoff scheme we investigate the QCD phase diagram and its dependence on the vector coupling strength $g_v$. We find that the first order chiral phase transition at moderate baryon chemical potentials and its critical point, a generic feature of most NJL-type models without vector coupling, disappear for sufficiently large values of $g_v$ that are consistent with lattice QCD results at imaginary chemical potential. The influence of non-zero $g_v$ on the curvature of the crossover boundary in the $T-\mu$ plane close to $\mu = 0$ is also examined.